Impulse producing circuit



Dec. 14, 1965 M E, MQHR IMPULSE PRODUCING CIRCUIT Filed D60. 20, 1943/A/VENTOR M. E. MOH/1" ATTORNEY United States Patent O 3,223,931lll/ilULSE PRODUCHNG ClRCUlll Milton E. Mohr, Summit, NJ., assignor toBell Telephone Laboratories, incorporated, New York, NSY., a corporationoi New York Filed Dec. 20, 1943, Ser. No. 514,997 3 Claims. (Cl.3282-154) The present invention relates to the production of electricalcurrent or voltage of stepped wave form for signaling, testing or otherpurposes.

The general object of the invention is to produce an output electricalwave varying in steps of different arnplitude in any one of severaldifferent orders as desired and to repeat the wave over and over asdesired.

In certain types of signaling or testing it is desired to have availablea wave which has diierent amplitudes definitely related to time but inan order which may not necessarily be ascending or descending but may beirregular. As one example, the wave may have four, tive or any number ofdeiinite amplitudes related in arithmetic or geometric proportions or inany other manner and occurring in time in the order l, 2, 3, 4 o1' 2, 4,l, 3 or in any other order as desired and repeating in the same orderindefinitely. The invention provides for generating such waves and forvarying their form or type at will, so that the same circuit is capableof producing a Wide range of wave forms.

The application of such a circuit to the testing of relays, vacuumtubes, gas-filled tubes or any circuit having threshold or marginaloperating characteristics will be obvious to those skilled in the art.Other uses might be to generate pulses for signaling and kindredpurposes.

In its more specic aspects, the embodiment to be disclosed herein forillustration employs a plurality of trigger tubes operating one at atime in a cycle which is repeated over and over and a secondary seriesof trigger tubes operating one at a time in unison with and undercontrol of the first plurality of tubes and having a com mon outputcircuit to which the secondary tubes are coupled through individualcouplings that permit a given fractional output of each to be applied tothe common output.

The nature of the invention and its various features and objects will bemore fully understood from the following detailed description togetherwith the accompanying drawing in which FIG. l is a schematic circuitdiagram of one illustrative embodiment of the invention and FIG. 2 showssample types of wave forms readily obtainable with the circuit of FIG.l.

Referring to FIG. l, the iirst plurality of trigger tubes mentionedabove comprises in this case the four tubes to 13 although any pluralnumber greater or less than four such tubes could be used as desired.The secondary series of tubes comprises the four tubes 14 to 17. All ofthese tubes are of the type in which a control grid, or equivalent,controls initiation of the discharge which thereafter persists until theplate circuit is interrupted or the plate voltage otherwise reducedbelow the sustaining value. One example of such trigger tube is agas-filled tube in which the discharge is carried by ionization. In thiscase heated cathodes are assumed although no heating circuit is shown.

All of the cathodes are connected together and to lead 18 which appliesbetween the cathodes and ground a pulsing voltage derived from theimpulser 19, which is in turn controlled by exciter 20 and constantfrequency driving oscillator 21. The impulser circuit puts out a voltageof the form indicated in the diagram adjacent lead 1S, comprisingnegative pulses of -150 volts peak value and some convenient length,such as 18 milliseconds for 3,223,231 Patented Dec. lll, 1965 example,separated by spaces of zero voltage lasting 2 milliseconds on the basisof a 50-cycle wave from source 21. The exciter 20 and impulser 19 ofthemselves form no part of the present invention and may be of any knownsuitable type, one example being given in Lundstrom- Schimpf applicationSerial No. 456,322, led August 27, 1942. Briefly, the exciter has a pairof vacuum tubes which are biased too far negative to transmit currentduring the negative half cycle of the control Wave from 21 but whichboth transmit current for a part of the positive half cycle, thearrangement being such that one of the tubes is caused by a phase delayin its grid circuit to begin to transmit slightly in advance of theother (2 milliseconds in advance, in this case). When the second tubebegins to transmit, its plate current cuts off the first tube byswinging the grid bias beyond cut-oit. The plate current of the iirsttube which iiows for a duration of 2 milliseconds interrupts the normalpassage of current through the cathode impulser by applying a highnegative bias to the grid of a tube in the cathode impulser 19. Thisimpulser supplies a regulated voltage of volts to the cathode lead 18 atall times except for the 2-millisecond periods of interruption.

All of the grids of the tubes 10 to 17 are connected through individualleak resistances (such as 70 and 72) to lead 22 which connects throughnegative bias battery 23 to the cathode lead 18.

The anodes of tubes 10 to 13 are individually connected to groundthrough resistors 24 to 27 and the plates of the tubes 14 to 17 may beindividually connected to resistors 28 to 31, each of which is providedwith a series of tapping points connectable to the output lead 32 whenthe corresponding selector switch 33 to 36 has been moved oit its firstor open circuit position and on to one of the contacts connected to atapping point of the resistor 28, 29, etc. The load terminals for takingoff the generated impulses are at 32 and 38 connected to the ends ofcoupling resistor 37.

A condenser-resistance timing circuit is connected between the anodecircuit of each tube in each row of tubes and the grid circuit of thenext. This comprises a condenser 4t) to 43 for the lower row in the gureand condenser 44 to 47 for the upper row together with the resistors 50to 53 and 54 to 57, the associated plate resistors 24 to 27 for thelower row of tubes and the grid leak resistors in each case. The purposeof these timing circuits is to condition the next succeeding tube in theseries for firing when the cathode impulser again applies -150 volts toall of the cathodes after an interruption period has restored thepreviously operated tube, as will be more fully described. Smallcondensers 61D and 61, one per tube, also assist in establishing thering conditions for the next tube as well as in suppressing transientsand preventing false operation. These small condensers are each in shuntacross the leak resistor and bias battery 23. One way in which thesecondensers prevent false firing is by off-setting the effect ofgrid-to-ground capacity which might produce a positive grid pulsesufficient to tire the tube in case the cathode potential is droppedvery abruptly.

A start key 65 consists of two halves, 65 and 65', which when closedshunt out the small condensers 60 and 61 associated with the grids oftubes 10 and 14, respectively, and connect the control grids directly tothe cathodes.

When the energizing circuit is iirst turned on and with key 65, 65 openit is possible that no tubes will be tired or that certain of the tubesmay tire irregularly. The purpose of the key 65 is to control the startof the sequence by causing tube 1li to iire repeatedly each time thecathodes are driven negative While the key is closed. Then, upon releaseof the key, the tubes will fire in the fixed sequence 1li, 11, 12, 13,10, etc. Such tubes of the secondary series 14 to 17 as have their platecircuits closed at the switches 33 to 36 will fire in unison with thecorresponding tubes of the primary series.

In explaining the voltage and time relations, only the primary series oftubes to 13 will be taken into account, since it is clear from what issaid above that the tubes 14 to 17 are individually controlled in theirring by the firing of the primary series.

Before the circuit is -started by pressing key 65, each condenser 40 to43 becomes practically fully charged during each firing period of 18milliseconds since the time constant of its circuit is about 11milliseconds. The 2- millisecond restoring period is to short to allowvery much of the charge to leak off. The voltage at the terminals ofthese condensers nearest the grids (lower plates in the drawing)therefore varies between limits of about -159 volts and -120 volts withrespect to ground so that the grid-to-cathode voltage is in every partof the cycle too far negative to allow the tubes to lire.

When key 65 is closed the grid of tube 10 is connected directly to itscathode so that tube 10 tires each time its cathode is driven negativeand is restored in the intervening periods. The drop of potential acrossplate resistor 24 when tube 10 is conducting is about 135 volts, thedrop `across the tube being only `about volts. Condenser 40 does not,therefore, charge to more than a few volts since the drop across thecircuit 40, 50, 70 is only the difference between the voltage acrosstube 10 and the voltage of battery 23. However, `as long as key 65 isheld closed tube 10 alone will continue to lire and its firing willresult in such a large potential drop across resistor 24 that tube 11cannot fire. As soon as the key 65 is opened, however, the existence ofonly the very small charge on condenser 40 and the absence of anypotential drop in resistor 24 will permit the tube 11 to tire becausethe distribution of potentials along the potentiometer 24, 40, 50, 70due to charging current into condenser 40 allows the grid to gosufficiently positive with respect to the cathode. Tube 11 will,therefore, re once and establish the necessary conditions in the circuit25, 41, 51, 72 to cause the next tube 12 to re in the next succeedingring period, and the tubes in this manner re in a closed cycle.

Considering tube 15 in the upper row, by way of example, the samevoltage conditions exist on its control grid and cathode as exist in thecase of tube 11 since the capacities and resistances in the interstagecircuit are the same in both cases. This is true of each of the stages.The upper tubes are, therefore, caused to re in the same sequence as thelower row of tubes.

The switches 33 to 36 can be set to any position at any time eitherduring the operation of the circuit or before starting it. In order togenerate current of the type indicated at a in FIG. 2, having impulsesof amplitudes 1, 0, 3, 2 in rotation, switches 33 to 36 are set onterminals 1, 0, 3 and 2. Other types of waves are indicated at b and cby way of example, these being of the form 1, 5, 3, 4 and 5, 0, 2, 3,respectively. Other types of waves will be obvious from the examplesgiven.

What is claimed is:

1. In a circuit for producing a wave of repetitive stepped form, aplurality of trigger tubes operating one after another in a closed cyclewith each tube initiating operation of the next, a secondary series oftubes operating one at a time in unison with and under control of saidplurality of trigger tubes, a common output circuit for all of the tubesof said secondary series, and connections from said common outputcircuit to the outputs of individual tubes of said secondary seriesincluding adjustable individual coupling means to apply a differentfractional part of the individual tube output current to said commonoutput circuit.

2. In an impulse producing circuit, a plurality of trigger tubesoperating in sequence in a closed cycle, a source of periodicallyinterrupted space current supply voltage for said tubes, couplingcircuitss between successive tubes for determining the order in whichsaid tubes fue, a second plurality of trigger tubes each tube of whichis paired with and is operated by a tube of the first-mentionedplurality, a common output circuit for all of the tubes of Isaid secondplurality and variable coupling impedances between each of saidlast-mentioned tubes and said common output for enabling differentfractional p0rtions of the output current of each of Asaid latter tubesto be applied to said common output circuit.

3. In an impulse producing circuit, a primary series and a secondaryseries of trigger tubes, means for ring one tube in each series inunison as pairs, a timing circuit connecting the anode of each primarytube to the control electrode of both tubes of the next pair todetermine the firing order, a source of periodically interrupted voltagefor driving the cathodes of all tubes in common to a negative potentialwith respect to ground to enable said tubes to fire and restore atperiodic times, resistors connecting the anodes of each tube to ground,a common output circuit for the tubes of the secondary series, andselective switches for varying in steps the point of connection betweenthe respective anode resistor of each tube in the secondary series andsaid common output circuit.

References Cited by the Examiner UNITED STATES PATENTS 1,932,589 10/1933Holden 250-27 2,089,430 8/1937' Roys et al Z50-27 2,099,065 11/ 1937Holden Z50-127 2,146,862 2/1939 Shumard 250-27 2,272,070 2/ 1942 Reeves250-27 2,300,999 11/ 1942 Williams 250-27 2,308,778 1/1943 Prince 250-272,369,662 2/ 1945 Deloraine et al. 250--27 2,373,134 4/ 1945 Massonneau250-27 2,398,771 4/1946 Compton 250-27 2,401,657 6/1946 Mumma 250-272,404,307 7/ 1946 Whitaker 250-27 2,422,583 6/ 1947 Mumma 250-27 ARTHURGAUSS, Primary Examiner.

ARTHUR W. CROCKER, CLARE M. WHITMAN,

JAMES L. BREWINK, Examiners.

1. IN A CIRCUIT FOR PRODUCING A WAVE OF REPETIVIE STEPPED FORM, APLURALITY OF TRIGGER TUBES OPERATING ONE AFTER ANOTHER IN A CLOSED CYCLEWITH EACH TUBE INITIATING OPERATION OF THE NEXT, A SECONDARY SERIES OFTUBES OPERATING ONE AT A TIME IN UNISON WITH AND UNDER CONTROL OF SAIDPLURALITY OF TRIGGER TUBES, A COMMON OUTPUT CIRCUIT FOR ALL OF THE TUBESOF SAID SECONDARY SERIES, AND CONNECTIONS FROM SAID COMMON OUTPUTCIRCUIT TO THE OUTPUTS OF INDIVIDUAL TUBES OF SAID SECONDARY SERIESINCLUDING ADJUSTABLE INDIVIDUAL COUPLING MEANS TO APPLY A DIFFERENTFRACTIONAL PART OF THE INDIVIDUAL TUBE OUTPUT CURRENT TO SAID COMMONOUTPUT CIRCUIT.